Population genomics of neotropical trees: identification of genes associated with natural selection in different phytophysiognomies

Abstract

Despite the central role that natural selection had in the formulation of modern evolutionary synthesis and the importance it continues to play in understanding the evolutionary histories of species, identification and study of genes under selection has always been of great difficulty, especially in non-model species. Selective pressure produces genotypes better adapted to local conditions. This evolutionary mechanism not always culminates in speciation but alternatively it may induce the formation of populations whose genotypes are adapted to local ecological conditions. Evidence of such adaptation have been observed between species that occur in regions of brazilian Savanna and Semideciduous Forest (BSF).How do behave populations of the same species subjected to different environmental conditions such as those found in Savanna and BSF? We assume that each of these environments have selective pressures that may favor different sets of alleles at each location (hypothesis 1), that local adaptation is based on small number of loci with high individual effect (hypothesis 2); and that the effect of these loci can manifest in early development of individuals as different adaptative values according to the environmental growing conditions (hypothesis 3). The evidence and understanding of this phenomenon is important for a better understanding of how individuals of same species can survive in different temperature, water availability and soil nutrition. This understanding is particularly important in the current scenario of climate change and water shortage. Furthermore, identification of the alleles associated with these conditions in native species may provide tools for the improvement of crop species of economic interest. The objective of this project is to identify loci that may be suffering distinct selective pressure in Savanna and BSF environments. Therefore, we'll perform common garden experiments with Savanna and BSF populations of five tree species, which will be evaluated to survival and growth of seedlings during six months. The species that provide evidence of local adaptation, with contrasting development measures between the growing conditions that simulate each of these environments will be selected to population genomics analysis with RADseq technique to identify loci with non-neutral behavior (outliers) for which we will seek to identify function by comparison with gene sequences database and correlation with observed phenotypic parameters. (AU)